1. Field of the Invention
This invention relates to a process and apparatus for handling a discharge of ash concentrate from a coal deashing system under a variety of operating conditions.
2. Description of the Prior Art
Various coal processing systems have been developed in the past wherein coal has been treated with one or more solvents and processed to separate the resulting insolubles from the soluble coal products.
An improved process for deashing coal liquefaction products is disclosed in U.S. patent application Ser. No. 838,021 filed Sept. 27, 1977 and assigned to the same assignee as the present invention. In said application, a feed mixture comprising soluble coal products, solvent and insoluble coal products is separated in a first separation zone maintained at an elevated temperature and pressure into a first heavy phase comprising insoluble coal products and some of the solvent and a first light phase. The insoluble coal products comprise the undissolved coal, mineral matter, other solid inorganic particulate matter and other such matter which is insoluble in the solvent solution under the operating conditions of the instant process.
The first heavy phase is withdrawn from the first separation zone and the pressure level is reduced at least 100 psig and preferably at least about 500 psig to vaporize the solvent and yield an ash concentrate composition in a dry, powdery form. The powdery ash concentrate composition can be made into aqueous slurries for use as a feed to subsequent processing equipment such as for example, gasifiers to recover additional hydrogen values or transported by mechanical means such as, for example, screw feeders or pneumatically.
Under certain conditions however, it has been found that the first heavy phase does not yield the desired, dry, powdery ash concentrate composition upon withdrawal and pressure reduction. Thus, sometimes the discharged first heavy phase is in the form of large chunks or deposits or a continuous extrusion of a semi-fluid which plugs the apparatus designed for handling a free flowing powder. Further, the deposits are hard to remove after formation in the transfer lines or vessels and require a tedious and expensive cleanout to restore operations.
Thus, it would be desirable to provide a means by which the first heavy phase can be handled when the first heavy phase does not form the dry, powdery composition.